Frequency-selecting receiving-circuit



F. E. PERNOT.

FREQUENCY SELECTING RECEIVING CIRCUIT.

APPLICATION man 05c. I9. 911.

1,36 Patented Jan. 25,1921.

MAIII WITNESSEQ A TTOR/VEIS FREDERICK E. PERNOT, 0F BERKELEY, CALIFORNIA, ASSIGNOIB 0F. ONE-THIRD TO GEORGE LOTHAINE GREVES, OF BERKELEY, CALIFORNIA...

FEEQUENCY-SELECTING RECEIVING-CIRCUIT.

nseasao.

Application filed December 19, 1917.

To all whom, it may concern:

Be it known that l, l nnninucit ll. lnan'or, a citizen oi the U nitcd States, and a resident of Berkeley, in the county of Alameda and State of (.alifornia, have invented new and useful improvements in Frequcncy-Solecting Receiving-Circuits, of which the following is a specification. 1

My invention relates to improvements in receiving circuits, and it consists in the com binations, constructions and arrangements herein described and claimed.

An object of my invention is to provide a receiving circuit tuned to receive one or more predetermined tone frequencies to the substantial exclusion of all other frequencies, thereby preventing interference.

A further object or my invention is to provide for the simultaneous reception ata single station of several tone frequencies from one or moresourccs.

Other objects and advantages will appear in the following specification am the novel features of the invention will he particularly pointed out in the appended claims.

My invention is illustrated in the accompanying drawing. forming a part ot this application, in which Figure l is a diagrammatic view showing the connections for a receiving circuit for a single tone frequency and Fig. 2 is a diagram of a circuit arranged to enable the receiving of a plurality of diliferentt-one frequencies, each independently of the others.

The receiving circuit which forms the subject of this invention has certain portions which are in ordinary use and these portions will be described in order that the com bination of the old elements and the new which form the new combination, will be readily understood.

Referring then to Figs. 1 and l have shown therein an aerial A which is con nected with one of the windings D of an aircore transformer. the opposite end being grounded at (in .he secondary winding E of the transformer is connected with one terminal of an audion l? the opposite terminal of the coil being connected to the audion as shown in the drawing. Condensers H and K are used in the circuit. the condenser H being interposed between the end of the coil E and audion and the condenser K be- Specification of Letters Patent.

Patented Jan. 25, 192i.

Serial No. 267,862.

ing bridged across the terminals of the Windrectly to the telephonereceiver as in ordi-' nary practice, is connected to an auxiliary circuit, which circuit'serves to separate the different group frequencies delivered to it by the audion. Each auxiliary circult as shown in single application in Figure 1, in-

eludes an inductance coil L which is connected at one end to the battery 'B,,the other end of the coil being connected with the wire V by means of a shiftable contact Z. A variable condenser (l is bridged across the terminals of the coil L. A telephone receiver It has one terminal connected with one end of the coil the other terminal being connected to an adjustable contact 7".

The operation of the circuit shown in Fig. 1 is as follows: The impulses are received by the aerial in the usual manner and are transmitted to the audion. The current from the-audion pulsates at the tone frequency of the sending set and servesto excite the circuit L, (l at this frequency. The circuit L, (I may be adjusted either by varying the capacity of the condenser C or by shifting the contacts Z or r.

in Fig. 2 l have shown an arrangement by which more than one operator may re -ceive at the same time. This is accomplished by providing a plurality of circuits similar to the circuit L. C, of Fig. 1. these circuits being shown at L C and at L (1,, lhe former having the receiver R, and the latter having the receiver R iliary receiver circuit is sensitive to one group frequency only. so that a single station may receive simultaneously a plurality of group frequencies.

Take this example: a succession of electrical impulses emanating from one station may be at a certain radio frequency such as one million cycles per second and at a certain group frequency, such as five hundred cycles per second. Another station Each auxmay send out impulses at the same radio frequency but at a group frequency of eight hundred cycles per second.

When these impulses reach the antenna A of the set in Fig. 2, they will of course be unintelligible until they pass the audion F It is now that the auxiliary circuits L and'L perform their separating actions. Each circuit being tuned to the group fre- 'quencies of five hundred and eight hundred cycles per second respectively, make only those impulses of these particular group frequencies audible in the respective telephones R and R While I have shown the receiving circuit connected with an audion it is obvious that any suitable equivalent such as a crystal or other detector, might be used without departing from the spirit of the invention.

also wish to call attention to the fact that the circuits as shown up to the auxiliary circuits, i. e. L, C, etc., are given only as examples, and that various changes might be made in said circuits without at all afiecting the principle upon which my improved receiving circuit operates.

lthough I have disclosed a receiving system which is used in connection with .some form of detector, the auxiliary re- -not limited to such use.

5t00d that in general the receivingcircuit may be applied wherever pulsations or alternations of electric nature exist and when.

ever it is desired to render the receiving circuit sensitive to only certain previously predetermined tone frequencies.

1. Wireless telegraph apparatus, comprising a receiving circuit, and an auxiliary cir cuit, including a telephone, a variable capacity condenser and an inductance coil in respect to which one terminal of each the receiving circuit and telephone is adjustable, for tuning the auxiliary circuitto a group-frequency.

2. Wireless telegraph apparatus, comprising a receiving circuit, and. a plurality of auxiliary circuits for segregating electrical impulses of difl'erent group frequencies arriving in common at the receiving circuit, each provided with an inductance connected at one terminal to the receiving circuit, telephones having one connection to said in'ductances, and another connection movable in respect to the inductances; and variable capacity condensers bridged across the inductance terminals.

3. The combination in a wireless telegraph apparatus, of a circuit for receiving electrical impulses of like radiofrequencies but different group-frequencies, means for segregating all impulses of like group frequencies, including inductance coils and variable capacity condensers bridged across parts of the receiving circuit, and means combined with said segregating means, for renderingsaid segregated group-frequencies intelligible, including telephones, each with a terminal adjustable along the companion inductance coil.

.' FREDERICK E. PERNOT. 

